Modeling the START transition in the budding yeast cell cycle
Fig 8
Simulation results of a few important START mutants.
Simulations of the following mutants and their steady state sizes (viability/inviability) and the active SBF/MBF complexes present are shown: (A) cln3Δ (only Bck2 activated forms are present; cells are very large), (B) bck2Δ (only Cln-activated forms are present; cells are slightly larger than WT), (C) swi6Δ (only Swi4dimers (SBFa5) present; cells are viable yet large), (D) swi4Δ swi6Δ (no SBF/MBF; cells are inviable), and (E) cln3Δ swi6Δ (only Swi4dimers (SBFa5) present; cells are viable yet large), (F) bck2Δ swi6Δ (no active SBF/MBF; cells are inviable), (G) swi4Δ (only MBF present; cells are very large), (H) mbp1Δ (only SBF present; cells are slightly larger than WT), (I) swi4Δ mbp1Δ (no SBF or MBF; cells are inviable), (J) GAL-WHI5-12A SWI6-SA4 (excess non-phosphorylable Whi5 inhibits MBF; cells are inviable), (K) whi5Δ (cells begin the cycle with less active SBF (SBFa1) instead of Whi5-bound inactive SBF, and get converted into more active forms by Clns (SBFa3). Active MBF is also present. Hence, cells are smaller than WT.), (L) bck2Δ cln3Δ (no active SBF/MBF; cells are inviable), (M) bck2Δ cln3Δ whi5Δ (deletion of Whi5 relieves SBF and the unmodified form of SBF (SBFa1) is consistently present and cells become viable), (N) CLN3-1 swi6Δ (only Swi4dimers (SBFa5) present; cells are viable yet large), (O) bck2Δ swi6Δ-SA4 (SBFa1, SBFa4, and MBFa present; cells are slightly larger than WT).